Re: [RFC PATCH] Use feature bit names in clearcpuid=

From: Thomas Gleixner
Date: Tue Sep 22 2020 - 04:03:09 EST

On Sun, Sep 20 2020 at 17:42, Borislav Petkov wrote:
> Hi,
> so tglx hates this clearcpuid= interface where you have to give the
> X86_FEATURE array indices in order to disable a feature bit for testing.
> Below is a first attempt (lightly tested in a VM only) to accept the bit
> names from /proc/cpuinfo too.
> I say "too" because not all feature bits have names and we would still
> have to support the numbers. Yeah, yuck.
> An exemplary cmdline would then be something like:
> clearcpuid=de,440,smca,succory,bmi1,3dnow ("succory" is wrong on
> purpose).
> and it says:
> [ 0.000000] Clearing CPUID bits: de 13:24 smca bmi1 3dnow
> Also, I'm thinking we should taint the kernel when this option is used.
> Thoughts?

Yes, instead of making it differently horrible, can we finally remove that
nonsense which should have never been there in the first place?